Expand parameterized testing documentation to mention try/await support and showcase helper pattern

[stmontgomery]

This expands a few places where we document parameterized testing APIs to mention try/await support and showcase a common pattern for sharing arguments between multiple tests.

Modifications:

• For each @Test macro which accepts arguments, mention that try and await are supported and that arguments are lazily evaluated.
• In the "Implementing parameterized tests" article, add a new section titled "Pass the same arguments to multiple test functions" showcasing the pattern of extracting common arguments to a separate property.
• Add a > Tip: callout within that new article section mentioning try/await support.

Checklist:

• Code and documentation should follow the style of the Style Guide.
• If public symbols are renamed or modified, DocC references should be updated.

Fixes rdar://130929060

[stmontgomery]

@swift-ci please test

[iamleeg]

This is useful guidance, thank you! I've suggested changing from passive to active voice throughout, and provided an example of what I mean.

[stmontgomery]

@swift-ci please test

[grynspan]

I don't feel strongly here, but do we need to repeat this for each overload or can we just document it in the article?

[grynspan]

Do we use tips otherwise in our documentation? I don't mind starting to use them, but I would like to get guidelines for when to use them instead of other callouts.

[grynspan]

@iamleeg Any advice?

[stmontgomery]

@swift-ci please test